The present invention relates to the separation of organics from liquid water, particularly to the use of hydrophobic aerogels as the separation medium, and more particularly aerogel materials with surfaces containing fluorine atoms which results in exceptional hydrophobicity, or the ability to repel liquid water.
A common approach to remove organic solvent pollutants from water is by filtration using porous materials. A variety of porous materials are useful for filtration but generally highly porous materials have the highest specific surface area and the highest absorption capacity. For this reason and because it is a relatively inexpensive product, granulated activated carbon (GAC) is usually selected as a filter medium; it is the standard for comparison.
Sol-gel derived porous materials, commonly known as aerogel or xerogels, are being developed for special filtration applications because they are chemically stable, they have very high specific surface areas, and they can readily be made as membranes for filtration application. These materials shown promise for separating organics from aqueous solutions because organic molecules have an affinity to adsorb on certain surfaces.
Aerogels and xerogels, hereafter referred to as aerogels, tend to be very hygroscopic (have affinity for water) due to the very small pores and the high surface areas within. Unmodified aerogels are generally incompatible with liquids and they will typically be destroyed upon contact with any liquids, including water. It is now known in the art that surfaces of the aerogel material can be chemically modified to make them more compatible with contracting water. However, the degree of hydrophobic nature (ability to shed water) is typically not quantified for such treated aerogels and the hydrophobic property usually changes with time. An improvement in the art will be an aerogel that has a distinct, quantified hydrophobic, nature and which will retain the property indefinitely under normal use conditions. Such an aerogel is described and claimed in U.S. Pat. No. 6,709,600, filed Sept. 21, 2001, and entitled “Method for Removing Organic Liquids from Aqueous Solutions and Mixtures.”
The present invention provides super-hydrophobic fluorine containing aerogel materials which exhibit exceptional hydrophobicity. These aerogel materials are compatible with various environments and enables many applications. The super-hydrophobic property of the aerogel material made in accordance with the present invention is achieved by formulating the aerogel using fluorine containing molecules either directly by addition in the sol-gel process, or by treating a standard dried aerogel material using the vapor of fluorine containing molecules.